JP2008308733A - Nickel powder coated with carbon and production method therefor - Google Patents
Nickel powder coated with carbon and production method therefor Download PDFInfo
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- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 title claims abstract description 148
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 81
- 229910052799 carbon Inorganic materials 0.000 title claims abstract description 81
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 26
- 239000007864 aqueous solution Substances 0.000 claims abstract description 31
- 150000001875 compounds Chemical class 0.000 claims abstract description 22
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 22
- 150000002815 nickel Chemical class 0.000 claims abstract description 20
- 239000002270 dispersing agent Substances 0.000 claims abstract description 16
- 229920000642 polymer Polymers 0.000 claims abstract description 16
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 claims abstract description 13
- 239000012299 nitrogen atmosphere Substances 0.000 claims abstract description 10
- 238000010438 heat treatment Methods 0.000 claims abstract description 9
- NBFQLHGCEMEQFN-UHFFFAOYSA-N N.[Ni] Chemical compound N.[Ni] NBFQLHGCEMEQFN-UHFFFAOYSA-N 0.000 claims abstract description 5
- 239000002245 particle Substances 0.000 claims description 64
- 238000000034 method Methods 0.000 claims description 24
- 239000011248 coating agent Substances 0.000 claims description 12
- 238000000576 coating method Methods 0.000 claims description 12
- 238000010304 firing Methods 0.000 claims description 11
- -1 ammonium ions Chemical class 0.000 claims description 7
- 239000000243 solution Substances 0.000 abstract description 35
- 239000000919 ceramic Substances 0.000 abstract description 9
- 239000003985 ceramic capacitor Substances 0.000 abstract description 8
- 239000007772 electrode material Substances 0.000 abstract description 6
- 239000000463 material Substances 0.000 abstract description 5
- 239000000758 substrate Substances 0.000 abstract description 4
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 abstract description 2
- 229910052759 nickel Inorganic materials 0.000 description 29
- 229910021586 Nickel(II) chloride Inorganic materials 0.000 description 21
- 229920002472 Starch Polymers 0.000 description 21
- QMMRZOWCJAIUJA-UHFFFAOYSA-L nickel dichloride Chemical compound Cl[Ni]Cl QMMRZOWCJAIUJA-UHFFFAOYSA-L 0.000 description 21
- 239000008107 starch Substances 0.000 description 21
- 235000019698 starch Nutrition 0.000 description 21
- 229910000008 nickel(II) carbonate Inorganic materials 0.000 description 20
- ZULUUIKRFGGGTL-UHFFFAOYSA-L nickel(ii) carbonate Chemical compound [Ni+2].[O-]C([O-])=O ZULUUIKRFGGGTL-UHFFFAOYSA-L 0.000 description 20
- 239000010410 layer Substances 0.000 description 19
- 239000010419 fine particle Substances 0.000 description 18
- 239000000126 substance Substances 0.000 description 18
- BFDHFSHZJLFAMC-UHFFFAOYSA-L nickel(ii) hydroxide Chemical compound [OH-].[OH-].[Ni+2] BFDHFSHZJLFAMC-UHFFFAOYSA-L 0.000 description 13
- UIIMBOGNXHQVGW-UHFFFAOYSA-M Sodium bicarbonate Chemical compound [Na+].OC([O-])=O UIIMBOGNXHQVGW-UHFFFAOYSA-M 0.000 description 12
- 239000000843 powder Substances 0.000 description 12
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 10
- 230000032798 delamination Effects 0.000 description 9
- 229910000480 nickel oxide Inorganic materials 0.000 description 9
- GNRSAWUEBMWBQH-UHFFFAOYSA-N oxonickel Chemical compound [Ni]=O GNRSAWUEBMWBQH-UHFFFAOYSA-N 0.000 description 9
- 238000009826 distribution Methods 0.000 description 8
- 239000007789 gas Substances 0.000 description 8
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 7
- 229910052717 sulfur Inorganic materials 0.000 description 7
- 239000011593 sulfur Substances 0.000 description 7
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 description 6
- 238000002441 X-ray diffraction Methods 0.000 description 6
- 229910003481 amorphous carbon Inorganic materials 0.000 description 6
- 239000012298 atmosphere Substances 0.000 description 6
- 238000006243 chemical reaction Methods 0.000 description 6
- 238000005245 sintering Methods 0.000 description 6
- 229910000030 sodium bicarbonate Inorganic materials 0.000 description 6
- 235000017557 sodium bicarbonate Nutrition 0.000 description 6
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 5
- 239000004202 carbamide Substances 0.000 description 5
- 238000002156 mixing Methods 0.000 description 4
- 239000012266 salt solution Substances 0.000 description 4
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 3
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 3
- 239000011362 coarse particle Substances 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 238000001035 drying Methods 0.000 description 3
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 3
- 229910000510 noble metal Inorganic materials 0.000 description 3
- 239000004215 Carbon black (E152) Substances 0.000 description 2
- 108010010803 Gelatin Proteins 0.000 description 2
- 229920003171 Poly (ethylene oxide) Polymers 0.000 description 2
- 239000004372 Polyvinyl alcohol Substances 0.000 description 2
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 2
- MQRWBMAEBQOWAF-UHFFFAOYSA-N acetic acid;nickel Chemical compound [Ni].CC(O)=O.CC(O)=O MQRWBMAEBQOWAF-UHFFFAOYSA-N 0.000 description 2
- 229910021529 ammonia Inorganic materials 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 229920000159 gelatin Polymers 0.000 description 2
- 239000008273 gelatin Substances 0.000 description 2
- 235000019322 gelatine Nutrition 0.000 description 2
- 235000011852 gelatine desserts Nutrition 0.000 description 2
- VKYKSIONXSXAKP-UHFFFAOYSA-N hexamethylenetetramine Chemical compound C1N(C2)CN3CN1CN2C3 VKYKSIONXSXAKP-UHFFFAOYSA-N 0.000 description 2
- 229930195733 hydrocarbon Natural products 0.000 description 2
- 150000002430 hydrocarbons Chemical class 0.000 description 2
- 239000011261 inert gas Substances 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 229940078494 nickel acetate Drugs 0.000 description 2
- 229920002401 polyacrylamide Polymers 0.000 description 2
- 229920002451 polyvinyl alcohol Polymers 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- XJDNKRIXUMDJCW-UHFFFAOYSA-J titanium tetrachloride Chemical compound Cl[Ti](Cl)(Cl)Cl XJDNKRIXUMDJCW-UHFFFAOYSA-J 0.000 description 2
- 229920002261 Corn starch Polymers 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 229920000881 Modified starch Polymers 0.000 description 1
- 239000004368 Modified starch Substances 0.000 description 1
- 229910021543 Nickel dioxide Inorganic materials 0.000 description 1
- 229920002125 Sokalan® Polymers 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 150000001721 carbon Chemical class 0.000 description 1
- 229920006319 cationized starch Polymers 0.000 description 1
- 239000011247 coating layer Substances 0.000 description 1
- 239000000084 colloidal system Substances 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 239000008120 corn starch Substances 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 238000006114 decarboxylation reaction Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 238000000635 electron micrograph Methods 0.000 description 1
- 239000000499 gel Substances 0.000 description 1
- 235000010299 hexamethylene tetramine Nutrition 0.000 description 1
- 239000004312 hexamethylene tetramine Substances 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 238000010030 laminating Methods 0.000 description 1
- YQCIWBXEVYWRCW-UHFFFAOYSA-N methane;sulfane Chemical compound C.S YQCIWBXEVYWRCW-UHFFFAOYSA-N 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 235000019426 modified starch Nutrition 0.000 description 1
- 150000002816 nickel compounds Chemical class 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- 229920005862 polyol Polymers 0.000 description 1
- 150000003077 polyols Chemical class 0.000 description 1
- 235000019422 polyvinyl alcohol Nutrition 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 229910000029 sodium carbonate Inorganic materials 0.000 description 1
- 238000007619 statistical method Methods 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
- 239000004408 titanium dioxide Substances 0.000 description 1
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
- 229920003169 water-soluble polymer Polymers 0.000 description 1
Abstract
Description
本発明は、積層セラミックコンデンサーや多層セラミック基板等の内部電極材料に適した炭素被覆ニッケル粉末およびその製造方法に関する。 The present invention relates to a carbon-coated nickel powder suitable for internal electrode materials such as a multilayer ceramic capacitor and a multilayer ceramic substrate, and a method for producing the same.
粒子径の小さなニッケル粉末は、厚膜導電体材料として積層セラミックコンデンサー（以下、ＭＬＣＣと呼ぶ）や多層セラミック基板等の電気回路形成のため使用されている。 Nickel powder having a small particle diameter is used as a thick film conductor material for forming an electric circuit such as a multilayer ceramic capacitor (hereinafter referred to as MLCC) or a multilayer ceramic substrate.
ＭＬＣＣはセラミック誘電体層と内部電極層とを交互に複数積層し、高温で焼成して一体化させた物である。ＭＬＣＣの作製方法は、内部電極材料である金属微粉末をバインダー中に分散させてペースト化し、該ペーストをセラミックグリーンシート上に印刷し、該印刷した基材を複数積層させて加熱圧着した後、還元雰囲気中で加熱焼成を行うことによって作製されている。 MLCC is a product in which a plurality of ceramic dielectric layers and internal electrode layers are alternately laminated and fired at a high temperature to be integrated. The MLCC is produced by dispersing metal fine powder as an internal electrode material in a binder to form a paste, printing the paste on a ceramic green sheet, laminating a plurality of the printed substrates, and thermocompression bonding, It is manufactured by heating and baking in a reducing atmosphere.
従来、ＭＬＣＣの内部電極材料としては、ＰｄやＡｇ−Ｐｄなどの貴金属粉末が使われてきた。貴金属は空気中で焼成できるので、ＭＬＣＣの作製に好適に用いることができるが、材料が高価という問題があった。このため、内部電極材料は比較的安価なニッケルに置き換えられてきている。 Conventionally, noble metal powders such as Pd and Ag-Pd have been used as internal electrode materials for MLCCs. Since the noble metal can be fired in the air, it can be suitably used for the production of MLCC, but there is a problem that the material is expensive. For this reason, the internal electrode material has been replaced with relatively inexpensive nickel.
しかし、ニッケル粉末は貴金属粉末を用いた場合に比べて、耐酸化性が劣るために、焼成時にニッケル粉末の一部が酸化されてしまい、セラミック誘電体層へ拡散するという欠点がある。また、焼成時の熱収縮率が大きいという問題もある。 However, since nickel powder is inferior in oxidation resistance compared with the case where noble metal powder is used, there is a drawback that a part of nickel powder is oxidized at the time of firing and diffuses into the ceramic dielectric layer. There is also a problem that the thermal shrinkage rate during firing is large.
ＭＬＣＣを作製する際の焼成温度は、例えばセラミック誘電体層の材料として広く使われているＢａＴｉＯ３を用いる場合には１１００℃以上の加熱を必要とする。しかし、ニッケル粉末の熱収縮開始温度は４００〜５００℃であるため、セラミック誘電体層と共焼成した際に、積層したセラミック誘電体層とニッケル層の間に熱収縮率の差から歪みが生じ、デラミネーション、クラックが生じてＭＬＣＣの性能が低下することになる。 For example, when BaTiO 3 widely used as a material for the ceramic dielectric layer is used, the firing temperature at the time of manufacturing the MLCC requires heating of 1100 ° C. or higher. However, since the thermal shrinkage starting temperature of nickel powder is 400 to 500 ° C., when co-fired with the ceramic dielectric layer, distortion occurs due to the difference in thermal shrinkage between the laminated ceramic dielectric layer and the nickel layer. As a result, delamination and cracks occur, and the performance of the MLCC deteriorates.
これまでにデラミネーションやクラックを防止する方法として種々の方法が提案されている。 Various methods have been proposed so far for preventing delamination and cracks.
特許文献１では、酸化物でニッケル粉末表面を被覆する手法として、塩化ニッケルガスと四塩化チタンガスを混合し、これらのガスと塩化ニッケルの還元ガスおよび四塩化チタンの酸化ガスとを反応させて、ニッケルと二酸化チタンを同時に合成した酸化チタン被覆ニッケル粉末を調製する方法が提案されている（特許文献１：特開２００５−２４００７６）。しかしながら、この方法で調製されたニッケル粉末ではニッケル粒子の表面だけでなくニッケル粒子の内部にも酸化物が形成されてしまうため、前記酸化物が、電極を形成した際に不純物として残留してしまう問題があると考えられる。さらに、塩化ニッケルをガス化させるための特別な真空装置を必要とする。 In Patent Document 1, as a method for coating the surface of nickel powder with an oxide, nickel chloride gas and titanium tetrachloride gas are mixed, and these gases are reacted with a reducing gas of nickel chloride and an oxidizing gas of titanium tetrachloride. A method for preparing a titanium oxide-coated nickel powder obtained by simultaneously synthesizing nickel and titanium dioxide has been proposed (Patent Document 1: JP-A-2005-240076). However, in the nickel powder prepared by this method, an oxide is formed not only on the surface of the nickel particle but also inside the nickel particle, so that the oxide remains as an impurity when the electrode is formed. There seems to be a problem. Furthermore, a special vacuum apparatus for gasifying nickel chloride is required.
また、特許文献２には、酸化物でニッケル粉末を被覆する方法として、オングミルやハイブリダイザーなどを用いて酸化物被覆ニッケル粉末を調製する方法が提案されている（特許文献２：特開平１１−３４３５０１）。しかし、オングミルやハイブリダイザーを用いて調製された酸化物被覆ニッケル粉末は、酸化物粒子とニッケル粒子との付着力が弱いために酸化物粒子がニッケル粒子から剥離しやすく、熱収縮率の改善効果は非常に低いと考えられる。 Patent Document 2 proposes a method of preparing an oxide-coated nickel powder using an ongmill, a hybridizer, or the like as a method of coating nickel powder with an oxide (Patent Document 2: Japanese Patent Laid-Open No. Hei 11-). 343501). However, the oxide-coated nickel powder prepared using ONGMILL or a hybridizer has a weak adhesion between the oxide particles and the nickel particles, so the oxide particles are easy to peel off from the nickel particles, and the heat shrinkage rate is improved. Is considered very low.
また、特許文献３ではニッケル金属微粉末の焼結開始温度を高くする方法として、ニッケル粉末に硫黄を含有させる技術が提案されている（特許文献３：特開１１−８０８１７）。しかしながら、特許文献３に記載されているような、気相水素還元によって調製された硫黄含有ニッケル粉末では、焼結時に硫黄が誘電体層に拡散し、誘電体層の電気的特性を劣化させるおそれがある。 Patent Document 3 proposes a technique for adding nickel powder to sulfur as a method for increasing the sintering start temperature of the nickel metal fine powder (Patent Document 3: Japanese Patent Laid-Open No. 11-80817). However, in the sulfur-containing nickel powder prepared by gas-phase hydrogen reduction as described in Patent Document 3, sulfur may diffuse into the dielectric layer during sintering, which may deteriorate the electrical characteristics of the dielectric layer. There is.
酸化物によるニッケル粉末の被覆や、ニッケル粉末への硫黄の含有による問題点を解決する手法として、ニッケル粉末を炭素で被覆する方法が提案されている。 As a technique for solving the problems caused by the coating of nickel powder with oxides and the inclusion of sulfur in the nickel powder, a method of coating the nickel powder with carbon has been proposed.
例えば、特許文献４ではニッケル粉末とヘキサンなどの炭化水素ガスを３００〜６００℃の温度条件下で接触させることによりニッケル粉末表面に炭素層を被覆するという方法が提案されている。（特許文献４：特開２００５−８９６０）この手法によって調製された炭素被覆ニッケル粉末をＭＬＣＣ内部電極材料に用いることにより、炭素に被覆していないニッケル粉末に比べて、焼結開始温度が高温側にシフトすることが明らかにされている。しかしながら、この方法では高温の炭化水素ガスでニッケル粉末を処理するために、特別な装置が必要である。 For example, Patent Document 4 proposes a method in which a carbon layer is coated on the surface of nickel powder by bringing nickel powder and hydrocarbon gas such as hexane into contact with each other under a temperature condition of 300 to 600 ° C. (Patent Document 4: JP-A-2005-8960) By using the carbon-coated nickel powder prepared by this method as the MLCC internal electrode material, the sintering start temperature is higher than that of the nickel powder not coated with carbon. It has been revealed that the shift to However, this method requires special equipment to treat nickel powder with hot hydrocarbon gas.
また、特許文献５ではニッケル粉末とポリオールを混合加熱して前記ニッケル粉末表面に炭素被覆層を形成させる方法が提案されている。（特許文献５：特開２００５−１５４９０４）この方法によって調製された炭素被覆ニッケル粉末を用いることにより、熱収縮特性を改善することが可能となっている。しかしながら、特許文献５に記載されているような混合加熱では、微粒のニッケル粒子の凝集を解き、該ニッケル粒子の表面を炭素で均一に被覆することは困難であると考えられる。そのため、微粒のニッケル粉末を炭素で均一に被覆するためには、ニッケル微粒子の調製と同時にニッケル微粒子の表面を炭素で被覆するという方法が好ましいと考えられる。 Patent Document 5 proposes a method in which nickel powder and polyol are mixed and heated to form a carbon coating layer on the surface of the nickel powder. (Patent Document 5: JP-A-2005-154904) By using the carbon-coated nickel powder prepared by this method, it is possible to improve the heat shrinkage characteristics. However, it is considered that it is difficult to remove the aggregation of fine nickel particles and uniformly coat the surfaces of the nickel particles with carbon by mixing heating as described in Patent Document 5. Therefore, in order to uniformly coat fine nickel powder with carbon, it is considered preferable to prepare a nickel fine particle and simultaneously coat the surface of the nickel fine particle with carbon.
一方、特許文献６には、ゼラチン被覆ニッケル化合物を形成した後、不活性ガス雰囲気下で加熱処理して、金属ニッケルと酸化ニッケルを含む微粒子に変換することが記載されている（特許文献６：特開２００７−１２６７４４号公報）。この調製方法では、不活性ガス雰囲気下での熱処理後には酸化ニッケルが混在するものであり、前記酸化ニッケルを金属ニッケルにするためには更に還元性ガス雰囲気下で加熱処理することが必要である。また、炭素を被覆した金属ニッケルを得ることは考慮されていない。 On the other hand, Patent Document 6 describes that after a gelatin-coated nickel compound is formed, heat treatment is performed in an inert gas atmosphere to convert it into fine particles containing metallic nickel and nickel oxide (Patent Document 6: JP, 2007-126744, A). In this preparation method, nickel oxide is mixed after heat treatment in an inert gas atmosphere, and in order to convert the nickel oxide into metallic nickel, it is necessary to further heat-treat in a reducing gas atmosphere. . Moreover, it is not considered to obtain metallic nickel coated with carbon.
ニッケル粉末の調製と炭素被覆を同時に行う技術として、以下の方法が報告されている。 The following methods have been reported as techniques for simultaneously preparing nickel powder and carbon coating.
非特許文献１（Ｃｈｅｍｉｓｔｒｙ Ｌｅｔｔｅｒｓ Ｖｏｌ．３５、Ｎｏ．７（２００６））には酢酸ニッケルを含む高分子分散剤水溶液にアンモニアを添加して加熱し、水酸化ニッケルコロイド水溶液を調製した後、該コロイド水溶液を乾燥させ、焼成することにより、炭素に被覆されたニッケル微粒子が調製できると報告されている。この方法によって、ニッケル微粒子を調製すると同時にニッケル微粒子表面を炭素で均一に被覆することができる。 In Non-Patent Document 1 (Chemistry Letters Vol. 35, No. 7 (2006)), ammonia is added to a polymer dispersant aqueous solution containing nickel acetate and heated to prepare a nickel hydroxide colloid aqueous solution. It has been reported that nickel fine particles coated with carbon can be prepared by drying and baking an aqueous solution. By this method, nickel fine particles can be prepared and at the same time the surface of the nickel fine particles can be uniformly coated with carbon.
近年、電子機器の小型化に伴い、ＭＬＣＣは小型化の傾向にあり、誘電体層および内部電極層の膜厚は１μｍ以下となってきている。そのため、薄層化に伴い小粒子径化が進んでおり、粒子径５０〜２００ｎｍのニッケル粉末が要求されている。 In recent years, with the miniaturization of electronic devices, MLCCs tend to be miniaturized, and the film thicknesses of the dielectric layer and the internal electrode layer have become 1 μm or less. For this reason, the particle diameter has been reduced along with the thinning, and nickel powder having a particle diameter of 50 to 200 nm is required.
しかしながら、非特許文献１には粒子径１０ｎｍ以下の炭素被覆ニッケル微粒子の調製方法しか記載されておらず、ＭＬＣＣに好適に用いることができる粒子径５０〜２００ｎｍの炭素被覆ニッケル粉末を調製することは困難であった。 However, Non-Patent Document 1 only describes a method for preparing carbon-coated nickel fine particles having a particle diameter of 10 nm or less, and preparing a carbon-coated nickel powder having a particle diameter of 50 to 200 nm that can be suitably used for MLCC It was difficult.
通常、ニッケル塩の水溶液にアンモニアを添加して加熱すると、非常に微細な水酸化ニッケル粒子が生成する。そのために非特許文献１においても微細な水酸化ニッケル粒子のみしか生成することができず、結果的に粒子径５０〜２００ｎｍの炭素被覆ニッケル粉末の調製が困難であったものと考えられる。 Usually, when ammonia is added to an aqueous nickel salt solution and heated, very fine nickel hydroxide particles are generated. Therefore, even in Non-Patent Document 1, only fine nickel hydroxide particles can be produced, and as a result, it is considered that preparation of carbon-coated nickel powder having a particle diameter of 50 to 200 nm was difficult.
近年、電子機器の小型化に伴い、ＭＬＣＣは小型化の傾向にあり、誘電体層および内部電極層の膜厚は１μｍ以下となってきている。そのため、薄層化に伴い小粒子径化が進んでおり、粒子径５０〜２００ｎｍのニッケル粉末が要求されている。また、デラミネーションやクラックの発生を防止できるニッケル粉末が求められている。 In recent years, with the miniaturization of electronic devices, MLCCs tend to be miniaturized, and the film thicknesses of the dielectric layer and the internal electrode layer have become 1 μm or less. For this reason, the particle diameter has been reduced along with the thinning, and nickel powder having a particle diameter of 50 to 200 nm is required. There is also a need for nickel powder that can prevent delamination and cracking.
しかしながら、上述のように従来のＭＬＣＣ内部電極用ニッケル粉末の調製方法では、酸化物によるニッケル粉末の被覆や、ニッケル粉末へ硫黄を含有させることにより、焼結開始温度を高温にシフトさせ、デラミネーションやクラックの発生を減らすことが可能となっているが、被覆した酸化物および含有させた硫黄が誘電体層に拡散してしまうといった問題があると考えられる。
また、酸化物や硫黄の誘電体層への拡散を解決する手法として炭素でニッケル粉末を被覆する手法が提案されているが、ＭＬＣＣに好適に用いられる粒子径５０〜２００ｎｍの炭素被覆ニッケル粉末を調製することは困難であった。
However, as described above, in the conventional method for preparing nickel powder for MLCC internal electrode, the sintering start temperature is shifted to a high temperature by coating nickel powder with oxide or by adding sulfur to nickel powder, thereby delamination. Although it is possible to reduce the occurrence of cracks and cracks, it is considered that there is a problem that the coated oxide and the contained sulfur diffuse into the dielectric layer.
Further, as a technique for solving the diffusion of oxides and sulfur into the dielectric layer, a technique of coating nickel powder with carbon has been proposed. A carbon-coated nickel powder having a particle diameter of 50 to 200 nm that is preferably used for MLCC is used. It was difficult to prepare.
本発明は炭素被覆ニッケル粉末の製法における上述した問題を解決するためになされたものであって、粒子径が５０〜２００ｎｍの範囲にあり、積層セラミックコンデンサー内部電極として好適に用いることができる炭素被覆ニッケル粉末およびその製造方法を提供することを目的とする。 The present invention has been made in order to solve the above-described problems in the production method of carbon-coated nickel powder, and has a particle diameter in the range of 50 to 200 nm and can be suitably used as an internal electrode of a multilayer ceramic capacitor. An object is to provide nickel powder and a method for producing the same.
前記技術的課題は、次のとおりの本発明によって達成することができる。 The technical problem can be achieved by the present invention as follows.
即ち、本発明は、炭素を被覆したニッケル粉末の製造方法であって、ニッケル塩を溶解させた高分子分散剤水溶液にアンモニウムイオンを生成する化合物を添加してニッケルアンモニア錯体を形成させ、次いで、炭酸イオンを生成する化合物を添加して加熱した後、水分を除去して乾燥物とした後、窒素雰囲気下で該乾燥物を焼成することを特徴とする炭素被覆ニッケル粉末の製造方法である（本発明１）。 That is, the present invention is a method for producing a nickel powder coated with carbon, wherein a compound that generates ammonium ions is added to a polymer dispersant aqueous solution in which a nickel salt is dissolved to form a nickel ammonia complex, A method for producing a carbon-coated nickel powder, comprising adding a compound that generates carbonate ions and heating, removing water to obtain a dried product, and then firing the dried product in a nitrogen atmosphere ( Invention 1).
また、本発明は、炭素被覆ニッケル粉末の平均粒子径が５０ｎｍ〜２００ｎｍである前記炭素被覆ニッケル粉末の製造方法である（本発明２）。 Moreover, this invention is a manufacturing method of the said carbon covering nickel powder whose average particle diameter of carbon covering nickel powder is 50 nm-200 nm (invention 2).
また、本発明は、炭素被覆ニッケル粉末の炭素被覆量が、１ｗｔ％〜７０ｗｔ％である前記炭素被覆ニッケル粉末の製造方法である（本発明３）。 Moreover, this invention is a manufacturing method of the said carbon coating nickel powder whose carbon coating amount of carbon coating nickel powder is 1 wt%-70 wt% (invention 3).
また、本発明は、平均粒子径が５０〜２００ｎｍであり、粒子径の標準偏差が０．５〜１００ｎｍであり、且つ、炭素含有量が１〜７０ｗｔ％であることを特徴とする炭素被覆ニッケル粉末である（本発明４）。 Further, the present invention provides a carbon-coated nickel characterized in that the average particle diameter is 50 to 200 nm, the standard deviation of the particle diameter is 0.5 to 100 nm, and the carbon content is 1 to 70 wt%. It is a powder (Invention 4).
本発明に係る炭素被覆ニッケル粉末の製造方法によって、簡便な方法で炭素を被覆したニッケル粉末を得ることができる。 By the method for producing carbon-coated nickel powder according to the present invention, nickel powder coated with carbon can be obtained by a simple method.
本発明に係る炭素被覆ニッケル粉末は、炭素が均一に被覆され、粒度分布に優れているので、積層セラミックコンデンサーに用いた場合に、デラミネーションやクラックを抑制することが期待できる。 Since the carbon-coated nickel powder according to the present invention is uniformly coated with carbon and has an excellent particle size distribution, it can be expected to suppress delamination and cracks when used in a multilayer ceramic capacitor.
本発明の構成をより詳しく説明すれば次の通りである。 The configuration of the present invention will be described in more detail as follows.
以下、本発明の炭素被覆ニッケル粉末の製造方法を詳細に説明する。 Hereinafter, the manufacturing method of the carbon covering nickel powder of this invention is demonstrated in detail.
この発明に従って炭素被覆ニッケル粉末を製造するとき、まずニッケル塩水溶液を用意する。ここでニッケル塩としては、たとえば塩化ニッケル、酢酸ニッケルなどの水に可溶性なニッケル塩を含む水溶液が用いられる。 When producing a carbon-coated nickel powder according to the present invention, an aqueous nickel salt solution is first prepared. Here, as the nickel salt, for example, an aqueous solution containing a nickel salt soluble in water such as nickel chloride and nickel acetate is used.
本発明の製造方法で用いられるニッケル塩水溶液の濃度は０．０５〜２モル／Ｌであることが好ましい。 The concentration of the nickel salt aqueous solution used in the production method of the present invention is preferably 0.05 to 2 mol / L.
次に、高分子分散剤水溶液を用意して、上記ニッケル塩水溶液に添加する。高分子分散剤としては、デンプン、ゼラチン、ポリビニルアルコール（ＰＶＡ）、ポリアクリル酸系ポリマー、ポリアクリルアミド（ＰＡＭ）、ポリエチレンオキシド（ＰＥＯ）等の水溶性高分子等であり、好ましくはデンプンを用いることができる。デンプンの種類は特に限定されず、とうもろこしデンプンなどの未加工デンプンや溶性デンプン、エステル化デンプンなどの加工デンプンを用いることができる。 Next, an aqueous polymer dispersant solution is prepared and added to the aqueous nickel salt solution. Examples of the polymer dispersing agent include starch, gelatin, polyvinyl alcohol (PVA), polyacrylic acid polymer, polyacrylamide (PAM), water-soluble polymer such as polyethylene oxide (PEO), and preferably starch is used. Can do. The kind of starch is not particularly limited, and raw starch such as corn starch, modified starch such as soluble starch and esterified starch can be used.
本発明の製造方法において、高分子分散剤の添加量はニッケル塩に対して質量で０．０５倍以上、好ましくはニッケル塩の質量の０．１〜２０倍であることが好適である。高分子分散剤の添加量が０．０５倍未満の場合には、焼成した際に炭酸ニッケルから脱炭酸して生成する酸化ニッケルを完全に還元できない。また、焼成後のニッケル粉末の焼結が進行しやすくなり、粒度分布が広くなってしまう。２０倍以上である場合には、焼成後に得られるニッケル粉末の炭素含有量が高くなり、ＭＬＣＣ内部電極用に好適に用いることが困難となる。 In the production method of the present invention, the addition amount of the polymer dispersant is 0.05 times or more by mass with respect to the nickel salt, and preferably 0.1 to 20 times the mass of the nickel salt. When the addition amount of the polymer dispersant is less than 0.05 times, nickel oxide produced by decarboxylation from nickel carbonate when baked cannot be completely reduced. Further, the sintering of the nickel powder after firing is likely to proceed, and the particle size distribution becomes wide. When it is 20 times or more, the carbon content of the nickel powder obtained after firing becomes high, and it becomes difficult to suitably use it for the MLCC internal electrode.
上記ニッケル塩と高分子分散剤の混合水溶液にアンモニウムイオンを生成する化合物を添加し、ニッケル塩水溶液を調製する。 A compound that generates ammonium ions is added to a mixed aqueous solution of the nickel salt and the polymer dispersant to prepare a nickel salt aqueous solution.
アンモニウムイオンを生成する化合物には、アンモニア水、ヘキサメチレンテトラミン、尿素などを用いることができる。 As the compound that generates ammonium ions, aqueous ammonia, hexamethylenetetramine, urea, or the like can be used.
本発明の製造方法で用いられるアンモニウムイオンを生成する化合物の添加量はニッケル塩１モルに対して、１〜１０モルであることが好ましい。添加量が１モル未満であると、ニッケルアンモニア錯体が十分に形成されず、ゲル状の炭酸ニッケル又は水酸化ニッケルが生成してしまい、焼成後の炭素被覆ニッケル粉末の粒度分布が広くなってしまう。 It is preferable that the addition amount of the compound which produces | generates the ammonium ion used with the manufacturing method of this invention is 1-10 mol with respect to 1 mol of nickel salts. When the addition amount is less than 1 mol, the nickel ammonia complex is not sufficiently formed, gelled nickel carbonate or nickel hydroxide is generated, and the particle size distribution of the carbon-coated nickel powder after firing becomes wide. .
次に、炭酸イオンを生成する化合物が用意される。炭酸イオンを生成する化合物としては、炭酸ナトリウム、炭酸水素ナトリウム、尿素などを含む水溶液が用いられる。 Next, a compound that generates carbonate ions is prepared. As the compound that generates carbonate ions, an aqueous solution containing sodium carbonate, sodium hydrogen carbonate, urea or the like is used.
本発明の製造方法において、炭酸イオンを生成する化合物の使用量は、ニッケル塩１モルに対して、１〜１０モルであることが好適である。炭酸イオンを生成する化合物の使用量が１モル未満であると、炭酸イオンを生成する化合物と反応しなかったニッケルアンモニア錯体から微細な水酸化ニッケルが生成してしまい、焼成後に得られる炭素被覆ニッケル粉末の粒子径が微細なものとなってしまう。 In the production method of the present invention, the amount of the compound that generates carbonate ions is preferably 1 to 10 mol with respect to 1 mol of the nickel salt. When the amount of the compound that generates carbonate ions is less than 1 mol, fine nickel hydroxide is generated from the nickel ammonia complex that has not reacted with the compound that generates carbonate ions, and the carbon-coated nickel obtained after firing The particle diameter of the powder becomes fine.
前記ニッケル塩水溶液と炭酸イオンを生成する化合物水溶液を混合して加熱することによって、炭酸ニッケル（塩基性炭酸ニッケルを含む）又は水酸化ニッケルのいずれか一種以上を含有する水溶液を調製することが好ましい。 It is preferable to prepare an aqueous solution containing at least one of nickel carbonate (including basic nickel carbonate) and nickel hydroxide by mixing and heating the aqueous nickel salt solution and the aqueous compound solution that generates carbonate ions. .
なお、本発明においては、アンモニウムイオンを生成する化合物及び炭酸イオンを生成する化合物の両方の機能を有する化合物として、尿素を用いることができる。尿素を用いることで、アンモニウムイオンを生成する化合物を添加する工程、炭酸イオンを生成する化合物を添加する工程を同時に行うことができ、この場合の添加量は、両方の工程の添加量の合計量とすればよい。 In the present invention, urea can be used as a compound having both functions of a compound that generates ammonium ions and a compound that generates carbonate ions. By using urea, the step of adding a compound that generates ammonium ions and the step of adding a compound that generates carbonate ions can be performed simultaneously. In this case, the amount added is the sum of the amounts added in both steps. And it is sufficient.
本発明の製造方法において、ニッケル塩水溶液と炭酸イオンを生成する化合物の反応温度は５０℃以上が好ましい。 In the production method of the present invention, the reaction temperature of the nickel salt aqueous solution and the compound that generates carbonate ions is preferably 50 ° C. or higher.
次に、上記反応溶液の水分を除去し、高分子分散剤と炭酸ニッケル及び／又は水酸化ニッケルの混合乾燥物を調製する。水洗、乾燥は、常法に従って行えばよい。 Next, the water of the reaction solution is removed, and a mixed dried product of the polymer dispersant and nickel carbonate and / or nickel hydroxide is prepared. Washing with water and drying may be performed according to a conventional method.
次に、上記乾燥物を雰囲気炉に入れて、窒素ガス雰囲気下で熱処理を行い、目的とする炭素被覆ニッケル粉末を調製する。 Next, the dried product is put in an atmosphere furnace and heat-treated in a nitrogen gas atmosphere to prepare a target carbon-coated nickel powder.
本発明の製造方法において、乾燥物の焼成は窒素雰囲気下で行い、焼成温度は３５０〜７００℃、焼成時間は１〜５時間が好ましい。 In the production method of the present invention, the dried product is fired in a nitrogen atmosphere, the firing temperature is preferably 350 to 700 ° C., and the firing time is preferably 1 to 5 hours.
本発明に係る炭素被覆ニッケル粉末は、平均粒子径が５０〜２００ｎｍであり、より好ましくは５０〜１５０ｎｍである。粒子径の標準偏差は０．５〜１００ｎｍが好ましく、より好ましくは０．５〜５０ｎｍである。炭素被覆ニッケル粉末の平均粒子径及び粒子径の標準偏差が前記範囲外の場合には、微細なニッケル粒子及び、粗大なニッケル粒子を含有することとなる。微細な粒子を含有するニッケル粉末を積層セラミックコンデンサーに用いた場合には、微細なニッケル粒子によって焼結温度が低温側にシフトしてしまい、デラミネーションやクラックを抑制することが困難となる。また、粗大な粒子を含有するニッケル粉末を積層セラミックコンデンサーに用いた場合では、粗大な粒子が電極間の誘電体層を突き破るため、デラミネーションやクラックを抑制することが困難となる。
本発明に係る炭素被覆ニッケル粉末の炭素含有量は１〜７０ｗｔ％であり、より好ましくは１０〜７０ｗｔ％である。炭素含有量が１ｗｔ％未満では、炭素でニッケル粉末を完全に覆うことができないため、デラミネーションやクラックを抑制することが困難となる。また炭素含有量が７０ｗｔ％より多いと、電極中のニッケル同士が接触しにくくなり、均一な電極層を形成することが困難となる。
The carbon-coated nickel powder according to the present invention has an average particle size of 50 to 200 nm, more preferably 50 to 150 nm. The standard deviation of the particle diameter is preferably 0.5 to 100 nm, more preferably 0.5 to 50 nm. When the average particle diameter and the standard deviation of the particle diameter of the carbon-coated nickel powder are out of the above ranges, fine nickel particles and coarse nickel particles are contained. When nickel powder containing fine particles is used in a multilayer ceramic capacitor, the sintering temperature is shifted to the low temperature side due to the fine nickel particles, making it difficult to suppress delamination and cracks. In addition, when nickel powder containing coarse particles is used in a multilayer ceramic capacitor, coarse particles break through the dielectric layer between the electrodes, making it difficult to suppress delamination and cracks.
The carbon content of the carbon-coated nickel powder according to the present invention is 1 to 70 wt%, more preferably 10 to 70 wt%. If the carbon content is less than 1 wt%, the nickel powder cannot be completely covered with carbon, and it becomes difficult to suppress delamination and cracks. Moreover, when there is more carbon content than 70 wt%, it will become difficult for the nickel in an electrode to contact, and it will become difficult to form a uniform electrode layer.
＜作用＞
本発明に係る炭素被覆ニッケル粉末の製造方法によって、粒子径５０〜２００ｎｍの炭素被覆ニッケル粉末が得られる理由を本発明者は以下のように考えている。
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The present inventor considers the reason why carbon-coated nickel powder having a particle diameter of 50 to 200 nm is obtained by the method for producing carbon-coated nickel powder according to the present invention as follows.
通常、高分子分散剤水溶液中でニッケル塩と炭酸水素ナトリウムなどの炭酸イオンを生成する化合物とを混合すると、反応が瞬時に進行し、ゲル状もしくは非常に微細な炭酸ニッケル微粒子含有水溶液しか得られない。 Normally, when a nickel salt and a compound that generates carbonate ions such as sodium hydrogen carbonate are mixed in an aqueous polymer dispersant solution, the reaction proceeds instantaneously, and only an aqueous solution containing gel fine particles or very fine nickel carbonate particles is obtained. Absent.
一方、本発明では、ニッケル塩を含む高分子分散剤の水溶液中にアンモニウムイオン生成する化合物を添加して、生成したアンモニアがニッケル塩と錯イオンを形成することにより、反応溶液中でのニッケルの溶解度を増加させる効果がある。反応溶液中でのニッケル溶解度が増加することにより、反応中の炭酸ニッケル、塩基性炭酸ニッケル又は水酸化ニッケル微粒子等は、溶解−析出を繰り返しつつ成長すると共に、高分子分散剤の効果によって、ある一定以上の粒子径成長が妨げられることにより、粗大な粒子が生成せず均一で所望の大きさの粒子径を有する炭酸ニッケル微粒子及び／又は水酸化ニッケル微粒子を得ることができると思われる。
このような本発明の製造方法によって得られる高分子分散剤を含有した炭酸ニッケル微粒子（塩基性炭酸ニッケル微粒子を含む）又は水酸化ニッケル微粒子を含有する反応溶液を乾燥することにより、高分子分散剤が炭酸ニッケル微粒子（塩基性炭酸ニッケル微粒子を含む）又は水酸化ニッケル微粒子などの粒子表面を被覆した状態の乾燥物が得られる。そして、その乾燥物を窒素中で焼成することによって炭酸ニッケル（塩基性炭酸ニッケルを含む）又は水酸化ニッケルは分解し酸化ニッケルとなり、また、高分子分散剤は炭化され炭素となる。生成した炭素の一部によって酸化ニッケルが還元されることにより、炭素被覆ニッケル粉末が調製されるものと考えている。
On the other hand, in the present invention, a compound that generates ammonium ions is added to an aqueous solution of a polymer dispersant containing a nickel salt, and the formed ammonia forms complex ions with the nickel salt. Has the effect of increasing solubility. By increasing the solubility of nickel in the reaction solution, nickel carbonate, basic nickel carbonate, nickel hydroxide fine particles, etc. during the reaction are grown while repeating dissolution-precipitation, and there are effects of the polymer dispersant. By hindering the growth of a certain particle diameter or more, it is considered that nickel carbonate fine particles and / or nickel hydroxide fine particles having a uniform and desired particle diameter can be obtained without generating coarse particles.
By drying the reaction solution containing nickel carbonate fine particles (including basic nickel carbonate fine particles) or nickel hydroxide fine particles containing the polymer dispersant obtained by the production method of the present invention, the polymer dispersant is obtained. Can obtain a dried product in which the surface of the particles such as nickel carbonate fine particles (including basic nickel carbonate fine particles) or nickel hydroxide fine particles is coated. Then, by baking the dried product in nitrogen, nickel carbonate (including basic nickel carbonate) or nickel hydroxide is decomposed to become nickel oxide, and the polymer dispersant is carbonized to become carbon. It is believed that the nickel oxide is reduced by a part of the produced carbon to prepare the carbon-coated nickel powder.
以下、本発明における実施例を示し、本発明を具体的に説明する。 Hereinafter, the present invention will be described in detail with reference to examples.
ニッケルの粒子形状および炭素の被覆状態は透過型電子顕微鏡ＴＥＭで観測した。粒子の平均粒子径は、電子顕微鏡写真に示される粒子３００個の粒子径をそれぞれ測定し、その個数平均値で示した。粒子径の標準偏差は、電子顕微鏡観察で撮影した画像の粒子に対して統計解析から求めた。 The particle shape of nickel and the coating state of carbon were observed with a transmission electron microscope TEM. The average particle diameter of the particles was measured by measuring the particle diameters of 300 particles shown in the electron micrograph, and indicated the number average value. The standard deviation of the particle diameter was obtained from statistical analysis on the particles of an image taken by electron microscope observation.
炭素含有量は、「カーボン・サルファーアナライザー：ＥＭＩＡ−２２００」（ＨＯＲＩＢＡ製）を使用して測定した。 The carbon content was measured using “Carbon Sulfur Analyzer: EMIA-2200” (manufactured by HORIBA).
粒子の構成は、「Ｘ線回折装置ＲＩＮＴ−２５００」（理学電機（株）製、管球：Ｃｕ）を用いて同定した。 The composition of the particles was identified using “X-ray diffractometer RINT-2500” (manufactured by Rigaku Corporation, tube: Cu).
＜実施例１＞
塩化ニッケル（和光純薬製）１．３ｇを２５ｍｌの純水に溶解して塩化ニッケル水溶液を調製した。溶性でんぷん（和光純薬製）５ｇを純水５０ｍｌに溶解してデンプン水溶液を調製した。塩化ニッケル水溶液とデンプン水溶液を混合撹拌した後、２５％アンモニア水（和光純薬製）を５ｇ添加した。この溶液に炭酸水素ナトリウム（和光純薬製）１．０ｇを２５ｍｌの純水に溶解した水溶液を添加し、その後９０℃で２時間加熱して、塩基性炭酸ニッケルを含有する溶液を調製した。その溶液を乾燥機に入れて８０℃で２０時間乾燥させた後、窒素雰囲気下で５５０℃で焼成した。
得られた粒子はＸ線回折より、金属ニッケルとアモルファスカーボンで構成されていることが確認された。ニッケルの平均粒子径は７１ｎｍであり、標準偏差が１４ｎｍと粒度分布が狭い粒子であった。ＴＥＭ観察を行ったところ、金属ニッケルの表面が炭素で完全に覆われていた。炭素含有量は粉末全体に対して６７ｗｔ％であった。
<Example 1>
A nickel chloride aqueous solution was prepared by dissolving 1.3 g of nickel chloride (manufactured by Wako Pure Chemical Industries) in 25 ml of pure water. An aqueous starch solution was prepared by dissolving 5 g of soluble starch (manufactured by Wako Pure Chemical Industries) in 50 ml of pure water. After mixing and stirring the nickel chloride aqueous solution and the starch aqueous solution, 5 g of 25% aqueous ammonia (manufactured by Wako Pure Chemical Industries) was added. An aqueous solution in which 1.0 g of sodium hydrogen carbonate (manufactured by Wako Pure Chemical Industries) was dissolved in 25 ml of pure water was added to this solution, and then heated at 90 ° C. for 2 hours to prepare a solution containing basic nickel carbonate. The solution was put into a dryer and dried at 80 ° C. for 20 hours, and then calcined at 550 ° C. in a nitrogen atmosphere.
The obtained particles were confirmed to be composed of metallic nickel and amorphous carbon by X-ray diffraction. Nickel had an average particle diameter of 71 nm and a standard deviation of 14 nm, which was a narrow particle size distribution. As a result of TEM observation, the surface of the metallic nickel was completely covered with carbon. The carbon content was 67 wt% with respect to the whole powder.
＜実施例２＞
塩化ニッケル（和光純薬製）１．３ｇを２５ｍｌの純水に溶解して塩化ニッケル水溶液を調製した。ワキシーアルファー（三和澱粉工業製）１ｇを純水５０ｍｌに溶解してデンプン水溶液を調製した。塩化ニッケル水溶液とデンプン水溶液を混合撹拌した後、２５％アンモニア水（和光純薬製）を３ｇ添加した。この溶液に炭酸水素ナトリウム（和光純薬製）１ｇを２５ｍｌの純水に溶解した水溶液を添加し、その後９０℃で２時間加熱して、塩基性炭酸ニッケルを含有する溶液を調製した。その溶液を乾燥機に入れて８０℃で２０時間乾燥させた後、窒素雰囲気下で５５０℃で焼成した。
Ｘ線回折より、金属ニッケルとアモルファスカーボンで構成されていた。ニッケルの平均粒子径は６８ｎｍあり、標準偏差が１３ｎｍと粒度分布が狭い粒子であった。ＴＥＭ観察を行ったところ、金属ニッケルの表面が炭素で完全に覆われていた。炭素含有量は粉末全体に対して３２ｗｔ％であった。
<Example 2>
A nickel chloride aqueous solution was prepared by dissolving 1.3 g of nickel chloride (manufactured by Wako Pure Chemical Industries) in 25 ml of pure water. An aqueous starch solution was prepared by dissolving 1 g of waxy alpha (manufactured by Sanwa Starch Industries) in 50 ml of pure water. After mixing and stirring the nickel chloride aqueous solution and the starch aqueous solution, 3 g of 25% aqueous ammonia (manufactured by Wako Pure Chemical Industries) was added. An aqueous solution in which 1 g of sodium hydrogen carbonate (manufactured by Wako Pure Chemical Industries) was dissolved in 25 ml of pure water was added to this solution, and then heated at 90 ° C. for 2 hours to prepare a solution containing basic nickel carbonate. The solution was put into a dryer and dried at 80 ° C. for 20 hours, and then calcined at 550 ° C. in a nitrogen atmosphere.
From X-ray diffraction, it was composed of metallic nickel and amorphous carbon. Nickel had an average particle diameter of 68 nm and a standard deviation of 13 nm, which was a narrow particle size distribution. As a result of TEM observation, the surface of the metallic nickel was completely covered with carbon. The carbon content was 32 wt% based on the entire powder.
＜実施例３＞
塩化ニッケル（和光純薬製）１．３ｇを２５ｍｌの純水に溶解して塩化ニッケル水溶液を調製した。カチオン化でんぷん（三和澱粉工業製）０．３ｇを純水５０ｍｌに溶解してデンプン水溶液を調製した。塩化ニッケル水溶液とデンプン水溶液を混合撹拌した。この溶液に尿素（和光純薬製）５ｇを２５ｍｌの純水に溶解した水溶液を添加し、その後９０℃で５時間加熱して、塩基性炭酸ニッケルを調製した。その溶液を乾燥機に入れて８０℃で２０時間乾燥させた後、窒素雰囲気下で５５０℃で焼成した。
Ｘ線回折より、金属ニッケルとアモルファスカーボンで構成されていた。ニッケルの平均粒子径は１０６ｎｍあり、標準偏差が４７ｎｍと粒度分布が狭い粒子であった。ＴＥＭ観察を行ったところ、金属ニッケルの表面が炭素で完全に覆われていた。炭素含有量は粉末全体に対して８ｗｔ％であった。
<Example 3>
A nickel chloride aqueous solution was prepared by dissolving 1.3 g of nickel chloride (manufactured by Wako Pure Chemical Industries) in 25 ml of pure water. An aqueous starch solution was prepared by dissolving 0.3 g of cationized starch (manufactured by Sanwa Starch Kogyo) in 50 ml of pure water. An aqueous nickel chloride solution and an aqueous starch solution were mixed and stirred. An aqueous solution in which 5 g of urea (manufactured by Wako Pure Chemical Industries) was dissolved in 25 ml of pure water was added to this solution, and then heated at 90 ° C. for 5 hours to prepare basic nickel carbonate. The solution was put into a dryer and dried at 80 ° C. for 20 hours, and then calcined at 550 ° C. in a nitrogen atmosphere.
From X-ray diffraction, it was composed of metallic nickel and amorphous carbon. Nickel had an average particle size of 106 nm and a standard deviation of 47 nm, which was a narrow particle size distribution. As a result of TEM observation, the surface of the metallic nickel was completely covered with carbon. The carbon content was 8 wt% with respect to the whole powder.
＜比較例１＞
塩化ニッケル（和光純薬製）１．３ｇを２５ｍｌの純水に溶解して塩化ニッケル水溶液を調製した。デンプン（和光純薬製）５ｇを純水５０ｍｌに溶解してデンプン水溶液を調製した。塩化ニッケル水溶液とデンプン水溶液を混合攪拌した。この溶液に炭酸水素ナトリウム（和光純薬製）１．０ｇを２５ｍｌの純水に溶解した水溶液を添加すると、瞬時に炭酸ニッケルが生成した。この溶液を８０℃の乾燥機で２０時間乾燥させた後、窒素雰囲気下で５５０℃で焼成した。
Ｘ線回折より、金属ニッケルとアモルファスカーボンで構成されていた。ニッケルの粒子は不定形であり、平均粒子径は３２７ｎｍであり、標準偏差が１９８ｎｍと粒度分布が広い粒子であった。ＴＥＭ観察を行ったところ、金属ニッケルの表面が炭素で完全に覆われていた。炭素含有量は粉末全体に対して６５ｗｔ％であった。
<Comparative Example 1>
A nickel chloride aqueous solution was prepared by dissolving 1.3 g of nickel chloride (manufactured by Wako Pure Chemical Industries) in 25 ml of pure water. An aqueous starch solution was prepared by dissolving 5 g of starch (manufactured by Wako Pure Chemical Industries) in 50 ml of pure water. An aqueous nickel chloride solution and an aqueous starch solution were mixed and stirred. When an aqueous solution obtained by dissolving 1.0 g of sodium hydrogen carbonate (manufactured by Wako Pure Chemical Industries, Ltd.) in 25 ml of pure water was added to this solution, nickel carbonate was instantaneously generated. This solution was dried at 80 ° C. for 20 hours and then calcined at 550 ° C. in a nitrogen atmosphere.
From X-ray diffraction, it was composed of metallic nickel and amorphous carbon. The nickel particles were indefinite, the average particle size was 327 nm, and the standard deviation was 198 nm. As a result of TEM observation, the surface of the metallic nickel was completely covered with carbon. The carbon content was 65 wt% with respect to the entire powder.
＜比較例２＞
塩化ニッケル（和光純薬製）１．３ｇを２５ｍｌの純水に溶解して塩化ニッケル水溶液を調製した。デンプン（和光純薬製）５ｇを純水５０ｍｌに溶解してデンプン水溶液を調製した。塩化ニッケル水溶液とデンプン水溶液を混合攪拌した。この溶液に２５％アンモニア水（和光純薬製）をｐＨが９になるまで滴下した後、９０℃に加熱し５時間攪拌して、水酸化ニッケルを含有する溶液を調製した。この溶液を８０℃の乾燥機で２０時間乾燥させた後、窒素雰囲気下で５５０℃で焼成した。
Ｘ線回折より、金属ニッケルとアモルファスカーボンで構成されていた。ニッケルの平均粒子径は８ｎｍであり、標準偏差が３ｎｍと粒度分布が狭い粒子であった。ＴＥＭ観察を行ったところ、金属ニッケルの表面が炭素で完全に覆われていた。炭素含有量は粉末全体に対して６７ｗｔ％であった。
<Comparative example 2>
A nickel chloride aqueous solution was prepared by dissolving 1.3 g of nickel chloride (manufactured by Wako Pure Chemical Industries) in 25 ml of pure water. An aqueous starch solution was prepared by dissolving 5 g of starch (manufactured by Wako Pure Chemical Industries) in 50 ml of pure water. An aqueous nickel chloride solution and an aqueous starch solution were mixed and stirred. To this solution, 25% aqueous ammonia (manufactured by Wako Pure Chemical Industries, Ltd.) was added dropwise until the pH reached 9, and then heated to 90 ° C. and stirred for 5 hours to prepare a solution containing nickel hydroxide. This solution was dried at 80 ° C. for 20 hours and then calcined at 550 ° C. in a nitrogen atmosphere.
From X-ray diffraction, it was composed of metallic nickel and amorphous carbon. The average particle size of nickel was 8 nm, and the standard deviation was 3 nm, and the particles had a narrow particle size distribution. As a result of TEM observation, the surface of the metallic nickel was completely covered with carbon. The carbon content was 67 wt% with respect to the whole powder.
＜比較例３＞
塩化ニッケル（和光純薬製）１．３ｇを２５ｍｌの純水に溶解して塩化ニッケル水溶液を調製した。この溶液に２５％アンモニア水（和光純薬製）を５ｇ添加した。この溶液に炭酸水素ナトリウム（和光純薬製）１．０ｇを２５ｍｌの純水に溶解した水溶液を添加し、その後９０℃で２時間加熱して、塩基性炭酸ニッケルを含有する溶液を調製した。その溶液を乾燥機に入れて８０℃で２０時間乾燥させた後、窒素雰囲気下で５５０℃で焼成した。
Ｘ線回折より、酸化ニッケルのみで構成されていた。ＴＥＭ観察を行ったところ、酸化ニッケル粒子表面には炭素は確認できなかった。炭素含有量は粉末全体に対して０ｗｔ％であった。
<Comparative Example 3>
A nickel chloride aqueous solution was prepared by dissolving 1.3 g of nickel chloride (manufactured by Wako Pure Chemical Industries) in 25 ml of pure water. To this solution, 5 g of 25% aqueous ammonia (manufactured by Wako Pure Chemical Industries) was added. An aqueous solution in which 1.0 g of sodium hydrogen carbonate (manufactured by Wako Pure Chemical Industries) was dissolved in 25 ml of pure water was added to this solution, and then heated at 90 ° C. for 2 hours to prepare a solution containing basic nickel carbonate. The solution was put into a dryer and dried at 80 ° C. for 20 hours, and then calcined at 550 ° C. in a nitrogen atmosphere.
From X-ray diffraction, it was composed only of nickel oxide. As a result of TEM observation, carbon was not confirmed on the surface of the nickel oxide particles. The carbon content was 0 wt% with respect to the entire powder.
本発明に係る炭素被覆ニッケル粉末は、炭素が均一に被覆され、粒度分布に優れているので、積層セラミックコンデンサーに用いた場合に、デラミネーションやクラックを抑制することが期待でき、ＭＬＣＣ内部電極層に好適に使用できることが期待される。 Since the carbon-coated nickel powder according to the present invention is uniformly coated with carbon and has an excellent particle size distribution, it can be expected to suppress delamination and cracks when used in a multilayer ceramic capacitor. MLCC internal electrode layer It is expected that it can be suitably used.
本発明に係る炭素被覆ニッケル粉末の製造方法によって、簡便な方法で炭素を被覆したニッケル粉末を得ることができる。
By the method for producing carbon-coated nickel powder according to the present invention, nickel powder coated with carbon can be obtained by a simple method.
Claims (4)
A carbon-coated nickel powder having an average particle diameter of 50 to 200 nm, a standard deviation of particle diameter of 0.5 to 100 nm, and a carbon content of 1 to 70 wt%.
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